package com.jfinalshop.ext.captcha;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.security.MessageDigest;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;

import com.jfinal.kit.StrKit;
import com.jfinal.render.Render;

/**
 * 验证码Render，这个验证码Render在构造函数里就已经创建好了随机码以及md5散列后的随机码。 调用方式如下： CaptchaRender
 * captchaRender = new CaptchaRender(); String md5RandonCode =
 * captchaRender.getMd5RandonCode(); 保存md5RandonCode到session、cookie或者其他地方
 * render(captchaRender); 基于JFinal的版本修改。
 * 
 */
public class CaptchaRender extends Render {
	@SuppressWarnings("unused")
	private static final long serialVersionUID = -7599510915228560611L;

	/**
	 * 随机码生成字典
	 */
	private static final String[] strArr = { "3", "4", "5", "6", "7", "8", "9",
			"A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M", "N", "P",
			"Q", "R", "S", "T", "U", "V", "W", "X", "Y" };

	/**
	 * 默认存储时使用的key,将md5散列后的随机码保存至session，cookie时使用。
	 */
	public static final String DEFAULT_CAPTCHA_MD5_CODE_KEY = "_CAPTCHA_MD5_CODE_";

	/**
	 * 图片宽度
	 */
	private final int imgWidth;

	/**
	 * 图片高度
	 */
	private final int imgHeight;

	/**
	 * 随机生成字符数量
	 */
	private final int imgRandNumber;

	/**
	 * 生成的随机码
	 */
	private final String randonCode;

	/**
	 * md5散列后的随机码
	 */
	private final String md5RandonCode;

	/**
	 * 构造函数,随机生成6个字符。
	 */
	public CaptchaRender() {
		this(6);
	}

	/**
	 * 构造函数
	 * 
	 * @param imgRandNumber
	 *            随机生成多少个字符,最少4个字符。
	 */
	public CaptchaRender(int imgRandNumber) {
		if (imgRandNumber < 4) {
			imgRandNumber = 4;
		}
		this.imgWidth = 16 * imgRandNumber + 15;
		this.imgHeight = 38;
		this.imgRandNumber = imgRandNumber;
		this.randonCode = generateRandonCode();
		this.md5RandonCode = encrypt(randonCode);
	}

	/**
	 * 获取md5散列后的验证码，调用发需妥善保存此验证码。
	 * 
	 * @return md5散列后的验证码
	 */
	public String getMd5RandonCode() {
		return this.md5RandonCode;
	}

	/**
	 * 依据字典生成随即码
	 * 
	 * @return 随机码
	 */
	private String generateRandonCode() {
		// 生成随机类
		Random random = new Random();
		String sRand = "";
		for (int i = 0; i < imgRandNumber; i++) {
			String rand = String.valueOf(strArr[random.nextInt(strArr.length)]);
			sRand += rand;
		}
		return sRand;
	}

	/**
	 * 渲染图片
	 */
	public void render() {
		BufferedImage image = new BufferedImage(imgWidth, imgHeight, BufferedImage.TYPE_INT_RGB);
		drawGraphic(image);
		response.setHeader("Pragma", "no-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		response.setContentType("image/jpeg");

		ServletOutputStream sos = null;
		try {
			sos = response.getOutputStream();
			ImageIO.write(image, "jpeg", sos);
		} catch (Exception e) {
			throw new RuntimeException(e);
		} finally {
			if (sos != null)
				try {
					sos.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
		}
	}

	/**
	 * 绘制验证码
	 * 
	 * @param image
	 *            BufferedImage对象
	 */
	private void drawGraphic(BufferedImage image) {
		// 获取图形上下文
		Graphics g = image.createGraphics();
		// 生成随机类
		Random random = new Random();
		// 设定背景色
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, imgWidth, imgHeight);
		// 设定字体
		g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

		// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 155; i++) {
			int x = random.nextInt(imgWidth);
			int y = random.nextInt(imgHeight);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}

		g.setFont(new Font("TimesRoman", Font.PLAIN, 20));
		// 取随机产生的认证码(img_randNumber位数字)
		for (int i = 0; i < imgRandNumber; i++) {
			String rand = String.valueOf(this.randonCode.charAt(i));
			// 将认证码显示到图象中
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
			g.drawString(rand, 16 * i + 6, 21);
		}
		// 图象生效
		g.dispose();
	}

	/**
	 * 生成随机颜色
	 * 
	 * @param fc
	 * @param bc
	 * @return 颜色对象
	 */
	private Color getRandColor(int fc, int bc) {
		Random random = new Random();
		if (fc > 255)
			fc = 255;
		if (bc > 255)
			bc = 255;
		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);
		return new Color(r, g, b);
	}

	/**
	 * 使用md5散列字符串
	 * 
	 * @param srcStr
	 *            输入的字符串
	 * @return 加密后的字符串
	 */
	private static final String encrypt(String srcStr) {
		try {
			String result = "";
			MessageDigest md = MessageDigest.getInstance("MD5");
			byte[] bytes = md.digest(srcStr.getBytes("utf-8"));
			for (byte b : bytes) {
				String hex = Integer.toHexString(b & 0xFF).toUpperCase();
				result += ((hex.length() == 1) ? "0" : "") + hex;
			}
			return result;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 验证码检查
	 * 
	 * @param md5RandomCode
	 *            md5散列后的验证码
	 * @param inputRandomCode
	 *            用户输入的验证码
	 * @return 若二者一致，返回true，否则返回false
	 */
	public static boolean validate(String md5RandomCode, String inputRandomCode) {
		if (StrKit.isBlank(md5RandomCode)
				|| StrKit.isBlank(inputRandomCode))
			return false;
		try {
			inputRandomCode = inputRandomCode.toUpperCase();
			inputRandomCode = encrypt(inputRandomCode);
			return inputRandomCode.equals(md5RandomCode);
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
	}

}
